Suitability of polydimethylsiloxane rods for the headspace sorptive extraction of polybrominated diphenyl ethers from water samples

Abstract

The suitability of an inexpensive polydimethylsiloxane (PDMS) sorbent, produced at industrial scale, for the extraction of polybrominated diphenyl ethers (PBDEs), from tetra- to hexabrominated congeners, from water samples was assessed. Experiments were carried out using samples spiked with a pentabromo diphenyl ether (pentaBDE) mixture, PDMS rods with a diameter of 2 mm and gas chromatography with micro-electron-capture detection (GC-micro-ECD). Influence of several variables on the efficiency of the enrichment step and the further desorption of the analytes was investigated in detail. The best performance was achieved in the headspace sorptive extraction (HSSE) mode, at 95 ºC, using 80 mL water samples containing a 30% of sodium chloride. Extractions were performed overnight using disposable PDMS rods with a length of 10 mm (31 L volume). Analytes were further recovered from the PDMS sorbent using just 1 mL of diethyl ether. This solvent was evaporated and extracts reconstituted with 25 L of isooctane. Under final working conditions absolute extraction efficiencies from 69 to 93% and enrichment factors higher than 2200 folds were achieved for all species. The proposed method provided acceptable precisions (relative standard deviations values under 12%), correlation coefficients higher than 0.998 and the yield of the HSSE process remained constant for different water samples.